Conventionally, there is known a technique in that, in order to monitor and control a load remotely, transmission signals including ON/OFF information of switches are transmitted through signal lines to turn on and off a relay for switching on and off power supply to a load.
This kind of a remote monitoring control system is configured to be a central control type, which includes: a terminal unit provided with an operation terminal device having a switch, and a control terminal device having a relay for switching on and off power supply to a load; and a central unit serving as a transmission unit. In the remote monitoring control system, a plurality of operation terminal devices and a plurality of control terminal devices may be provided. The transmission unit, the operation terminal device, and the control terminal device are connected through two-wired signal lines, and the transmission unit can recognize the operation terminal device and the control terminal device individually by using a terminal address set for each of the operation terminal device and the control terminal device.
Further, the transmission unit is provided with a memory storing a control table that serves as a data table in which the operation terminal devices are associated with the control terminal devices through addresses. When receiving the ON/OFF information of the switch from any of the operation terminal devices through transmission signals (using time division multiplex transmission signals), the transmission unit transmits an instruction for turning on and off a relay to the control terminal device associated with the operation terminal device by the control table through the transmission signals. And then, the control terminal device receiving the instruction turns on and off the relay. Thus, the load is controlled according to ON/OFF operations of the switch.
Such a remote monitoring control system includes a monitor and control apparatus capable of monitoring and controlling multiple loads at one place, the monitor and control apparatus being connected with signal lines (see, e.g., Japanese Patent Laid-open Application No. 10-243478, Patent Document 1).
The monitor and control apparatus described in Patent Documents 1 is provided with a body including: a display part having a liquid crystal display; and an operation part having transparent touch switches that are arranged to be superimposed on a screen of the display part. By touching the switches displayed on the screen of the display part, a user can control loads corresponding to the switches. Moreover, operation conditions of the respective loads as a control target are displayed on the display part. In the monitor and control apparatus, the user can manipulate multiple switches by changing the contents displayed on the display part, which reduces a space to be occupied by the switches compared with the case where the multiple switches are disposed individually.
A terminal unit, used for a remote monitoring control system by being connected with signal lines, includes the display part and the operation part as described in the above monitor and control apparatus. The terminal unit is, as shown in FIG. 10A, generally attached to an installation surface such as a wall in such manner that a front face of a body 5′ provided with a display part 2′ and an operation part 3′ is exposed and a rear portion of the body 5′ is inserted into a mounting hole H2 (see FIG. 11) that is opened in the installation surface. In fitting this kind of the terminal unit 1′, an embedded box for fitting an embedded-type wiring accessory is used. Specifically, the terminal unit 1′ is attached to the wall by fixing the body 5′ in the embedded box SB that is embedded in the wall as shown in FIG. 11. In this way, the display part 2′ and the operation part 3′ in the front side of the body 5′ can be recognized visually and operated, while minimizing an amount of a protrusion thereof from the wall surface W0 (see, e.g., Japanese Patent Laid-open Application No. 2007-251671, Patent Document 2).
In the terminal unit 1′ with such configuration, terminal sections T1 to T6 for connecting signal lines or the like are usually provided in the rear face of the body 5′ as shown in FIG. 10B. Since the signal lines are routed within the mounting hole H2, good appearance can be obtained when the terminal unit 1′ is attached to the installation surface. The terminal sections T1 to T6 are each provided with: a connecting terminal 21 having a terminal strip 21a and a terminal screw 21b; and an insulating wall 22 provided erectly between the adjacent connecting terminals 21, wherein the connecting terminal 21 and the insulating wall are protruded from the rear face of the body 5′. Therefore, between the rear face of the body 5′ and the bottom surface of the mounting hole H2 (the bottom surface of the embedded box SB), there is provided a space for routing the signal lines connected with the terminal boxes T1 to T6 around the terminal boxes T1 to T6. For this reason, as shown in FIG. 11, a depth dimension of the mounting hole H2 opened in the installation surface needs to be larger than a dimension “α” obtained by adding a height dimension of the terminal sections T1 to T6 (the protruding amount thereof from the rear face of the body 5′) to a thickness dimension from the installation surface to the rear face of the body 5′ (in the forward and backward direction) in the state where the body 5′ is attached to the installation surface.
The depth dimension of the mounting hole H2, however, are restricted by such as a depth dimension of the embedded box SB embedded in the wall. Thus, the dimension “α”, which is an amount of inserting the body 5′ into the mounting hole H2, is restricted (“α” is 30 mm or less in the example of FIG. 11), so that a depth dimension (in the forward and backward direction) of the body 5′ is hard to be increased. On the other hand, the monitor and control apparatus is desired to be multi-functionalized, for example, by adding an address setting function. As described above, however, the depth dimension of the body 5′ is restricted, which limits a volume of the body 5′. Accordingly, the number of components accommodated in the body is hard to be increased, which makes it difficult to have the monitor and control apparatus multi-functionalized. Besides, there is another disadvantage in that the high-density arrangement of the components in the body deteriorates heat dissipation properties.